In the related art, a technology is known in which a countermeasure is considered when a switching element configuring an inverter circuit fails in a motor control device which controls a motor by using the inverter circuit. For example, JP-A-2011-155708 discloses a motor control device which aims to appropriately cut off a connection of a closed loop which is generated by a short-circuit failure of a switching element. The motor control device includes a motor, an inverter which drives the motor, a current cut-off mechanism which cuts off a connection between the motor and the inverter. In addition, the motor control device performs control of the motor which turns on all switching elements before cut-off of the current cut-off mechanism is performed, in a case where a current sensor senses a short-circuit failure of a high side switching element of the inverter.
In addition, JP-A-2009-274686 discloses an electric power steering device which aims to avoid that a closed circuit is formed and steering assist force or electromagnetic brake that a driver does not intend are generated, in a short time, in a case where an inverter operates abnormally and assist stops. The electric power steering device includes an inverter which calculates a current command value on the basis of at least steering torque and vehicle speed, and supplies a motor phase current to each phase of the motor that provides the steering assist force to a steering mechanism on the basis of the current command value. In addition, the electric power steering device is provided with a first FET group on each phase supply path through which the motor phase current is supplied to the motor, and turns off a second FET group and the first FET group which configure the inverter, when abnormality of the inverter is detected.
In addition, JP-A-2011-239489 discloses a motor drive device which aims to prevent a semiconductor switching element for fail safe from being broken down by a spike voltage by using simple circuit configuration and control operation. In a case where abnormality is detected, the motor drive device turns off all the respective semiconductor switching elements of an inverter circuit, and thereafter, turns off all the respective semiconductor switching elements of a fail safe circuit at a point of time when a predetermined time passes.